a. Field of the Invention
The invention relates to an antenna set and an isolation enhancement method for use with different systems having dual-band antennas, where the dual-band antennas achieve high isolation when the different systems operate in an identical frequency band.
b. Description of the Related Art
An antenna is a key component for wireless communications systems. Because significant progress has been made on multiple entry/exit systems and integrated access devices, the number of antennas provided for a single apparatus is increased by several times to result in antenna coupling effects and thus reduce radiation efficiency. Besides, signal interference among different antenna systems may occur, and the signal interference is particularly severe when different antenna systems operate in an identical frequency band. Accordingly, it is desirable to design an antenna system confined in a limited space to have high radiation efficiency and isolation, which is the main subject of the invention.
In conventional wireless communications systems, communication bands of 2.4 GHz-2.5 GHz and 5.15 GHz-5.85 GHz are reserved for a wireless communication protocol 802.11ac for faster communications; however, these communication bands are open, and the communication band of 2.4 GHz-2.5 GHz is also available to other wireless communication interfaces such as blue tooth, cell phone, etc.
As illustrated in FIG. 1, a conventional dual-band antenna set 100 includes a first dual-band antenna 101 and a second dual-band antenna 102 that are the same in structure and characteristic.
In case the right-side second dual-band antenna 102 serves as a excitation source, an induced electric field may be formed to influence the left-side first dual-band antenna 101. Note since a low-frequency band of 2.4-2.5 GHz is in open use, the first dual-band antenna 101 is influenced by resonance effects induced by the second dual-band antenna 102 when the antennas 101 and 102 operate in an identical frequency band. The distribution of dense hatched areas illustrated in FIG. 1 indicates low-frequency signal interference is more significant when the antennas 101 and 102 operate in an identical frequency band.
Because the separation provided by passive elements such as filters fails to resolve the signal interference occurs in an identical frequency band, the amount of coupling between antennas is reduced to decrease the signal interference caused by other system operating in the same frequency band. Accordingly, it is highly desirable to provide an antenna system with high antenna isolation and improved radiation efficiency.